1. Field of the Invention
The present invention relates to a variable venturi carburetor for an internal combustion engine (hereinafter referred to as "engine") which can supply fuel at appropriate air-fuel ratio regardless of changes in the temperature of the fuel by utilizing constant negative pressure of the venturi portion.
2. Description of the Prior Art
In a conventional variable venturi carburetor for an engine, the fuel is caused to evaporate as the temperature thereof rises, leading to generation of bubbles of vapor in the fuel liquid. When the fuel containing such bubbles reaches a main fuel jet, the bubbles stay in an annular clearance between the main fuel jet and a metering needle to prevent normal flowing of the fuel since the area of the clearance is small. On account of this, the fuel cannot be supplied to the engine under appropriate air-fuel ratio, leading to a bad condition such as stoppage of the engine.
Further, during idling of the engine in which the volume of intake air is small, the area of the annular clearance between the main fuel jet and the metering needle becomes remarkably small, and especially when the temperature of the fuel is low, the flow of the fuel is decreased by viscosity, leading to inappropriate air-fuel ratio of the fuel to be supplied to the engine. Still further, it is difficult to obtain increased flow of the fuel for starting of the engine which requires an enriched mixture.